We have previously identified that PGP9.5 is frequently overexpressed in lung cancers. We have also used yeast two-hybrid assay to identify genes that interact with PGP9.5. We recently showed that three genes, JAB1, UBC9 and RanBPM, are associated with PGP9.5 both in vitro and in vivo. Site-directed mutagenesis method is being used to determine the regions of PGP9.5 protein that interact with these factors. We are also also in the process of developing a mouse model that allows for tissue specific expression of PGP.5 in the small airway of the lung to determine the role of PGP9.5 in lung tumorigenesis.